Evaluations of Leaf Area Index and Biomass of Soybean Canopies using Spectral Reflectivity

Abstract

Non-attach and non-destructive measuring method for estimating leaf area index (LAI) and biomass (top dry weight) of crops was applied for soybean canopy using portable spectroradiometer under natural conditions in the western Japan.
In this paper, we tried to find the most effective band or index suitable for estimating LAI and biomass.
1) The most effective index of spectral reflection characteristics for estimating the leaf area index of soybean canopy is R_850nm/R_650nm. The regression equation is LAI=0.250(R_850nm/R_650nm)-0.149. In this case, the correlation coefficient is 0.95.
2) The most effective index of spectral reflection charateristics for estimating the biomass in the duration from the early growth stage to the early seed development stage is R_850nm/R_650nm. The regression equation is biomass (top dry weight, g·m-2)=21.6(R_850nm/R_650nm)-42.1. The correlation coefficient is 0.96.
3) The effective index of spectral reflection characteristics for estimating the biomass in the duration from the middle seed development stage to the yellow ripe stage is R_450nm/R_1050nm. The regression equation is Biomass (top dry weight, g·m^-2)=-9070(R_450nm/R_1050nm)+921.8. The correlation coefficient is -0.85.